1. Field of the Invention
The invention relates to a projector, and more particularly to a projector with reduced power of an emitting lamp in a blanking mode.
2. Description of the Related Art
The conventional digital light processing (DLP) projector includes a lamp, an optical engine and a lens. The optical engine has a digital micro-mirror device (DMD), multiple reflective devices, a color wheel and a light pipe. The lamp emits a light ray. The light ray emitted from the lamp passes through the color wheel, which generates at least three primary-color light rays. The three primary-color light rays are conducted by the light pipe, and then enter the reflective devices. Thereafter, the three primary-color light rays reflected from the reflective devices are incident to the DMD. When the projector is in a normal mode, the three primary-color light rays are reflected by the DMD and pass through the lens, and then a projecting image is projected onto a screen outside the projector.
In general, the projector further has a blanking mode in addition to the above-mentioned normal mode. Since the lamp of the projector is a high brightness bulb set, the lamp cannot be immediately turned on of off because a predetermined period of time is required to either preheat after the lamp is turned on, or dissipate heat after the lamp is turned off. Consequently, the lamp of the projector is designed to have a blanking mode, in which the projector temporarily stops outputting the projecting image onto the screen. When the projector is in the blanking mode, no image is displayed on the screen. The operation of the conventional DLP projector in the blanking mode is such that all of the incident light rays to the DMD are reflected to an inner wall of the optical engine without being projecting out of the DLP projector by rotating the mirror angles of the micro-mirrors of the DMD.
However, when the DLP projector is in the blanking mode, all of the light rays are reflected from the DMD to the inner wall of the optical engine, thereby causing an overheating condition in the optical engine. Since the optical engine is a closed chamber and the light rays are reflected multiple times in the closed chamber after they are reflected by the inner wall, the temperature of the optical engine sequentially rises and the energy is thus wasted.
In addition, the problem of overheating of the optical engine also may occur in the blanking mode in the conventional transmittive LCD projector. In the blanking mode, the ploarizer of the LCD (liquid crystal display) panel blocks all of the light rays, and the temperature of the LCD projector keeps on rising accordingly. When the temperature of the DLP projector or LCD projector is too high, error operations will be caused or even the elements will be burn out. Consequently, it is quite necessary to provide a projector capable of solving the problems of overheating and energy wasting.